From: Sean Christopherson <seanjc@xxxxxxxxxx>
Subject: hugetlbfs: fix off-by-one error in hugetlb_vmdelete_list()
Pass "end - 1" instead of "end" when walking the interval tree in
hugetlb_vmdelete_list() to fix an inclusive vs. exclusive bug. The two
callers that pass a non-zero "end" treat it as exclusive, whereas the
interval tree iterator expects an inclusive "last". E.g. punching a hole
in a file that precisely matches the size of a single hugepage, with a vma
starting right on the boundary, will result in unmap_hugepage_range()
being called twice, with the second call having start==end.
The off-by-one error doesn't cause functional problems as
__unmap_hugepage_range() turns into a massive nop due to short-circuiting
its for-loop on "address < end". But, the mmu_notifier invocations to
invalid_range_{start,end}() are passed a bogus zero-sized range, which may
be unexpected behavior for secondary MMUs.
The bug was exposed by commit ed922739c919 ("KVM: Use interval tree to do
fast hva lookup in memslots"), currently queued in the KVM tree for 5.17,
which added a WARN to detect ranges with start==end.
Link: https://lkml.kernel.org/r/20211228234257.1926057-1-seanjc@xxxxxxxxxx
Fixes: 1bfad99ab425 ("hugetlbfs: hugetlb_vmtruncate_list() needs to take a range to delete")
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Reported-by: syzbot+4e697fe80a31aa7efe21@xxxxxxxxxxxxxxxxxxxxxxxxx
Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/hugetlbfs/inode.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
--- a/fs/hugetlbfs/inode.c~hugetlbfs-fix-off-by-one-error-in-hugetlb_vmdelete_list
+++ a/fs/hugetlbfs/inode.c
@@ -409,10 +409,11 @@ hugetlb_vmdelete_list(struct rb_root_cac
struct vm_area_struct *vma;
/*
- * end == 0 indicates that the entire range after
- * start should be unmapped.
+ * end == 0 indicates that the entire range after start should be
+ * unmapped. Note, end is exclusive, whereas the interval tree takes
+ * an inclusive "last".
*/
- vma_interval_tree_foreach(vma, root, start, end ? end : ULONG_MAX) {
+ vma_interval_tree_foreach(vma, root, start, end ? end - 1 : ULONG_MAX) {
unsigned long v_offset;
unsigned long v_end;
_
